1. Field of the Invention
The present invention generally relates to lithography, and more particularly to fluid transport where containment of a primary fluid is of paramount importance.
2. Related Art
A lithographic apparatus is a machine that applies a pattern onto a substrate, usually onto a target portion of the substrate. A lithographic apparatus can be used, for example, in the manufacture of integrated circuits (ICs). In that instance, a patterning device, which is alternatively referred to as a mask or a reticle, can be used to create a circuit pattern formed on an individual layer of the IC. The pattern can be transferred onto the target portion (e.g., comprising part of, one, or several dies) of the substrate (e.g., a silicon wafer). Transfer of the pattern is typically via imaging the pattern onto a layer of radiation-sensitive material (resist) on the substrate. In general, a single substrate will contain a network of adjacent target portions that are patterned. Known lithographic apparatus include steppers, in which each individual target portion is irradiated by exposing an entire pattern onto the target portion at one time, and scanners, in which each target portion is irradiated by scanning the pattern through a radiation beam in a given direction (the “scanning” direction) while synchronously scanning the substrate parallel or anti-parallel to this direction. It is also possible to transfer the pattern from the patterning device to the substrate by imprinting the pattern onto the substrate.
Within the lithographic apparatus, hydrogen gas is used for various processes. Hydrogen is hazardous, so for safety concerns, the tubing transporting the hydrogen must be rigid to resist punctures and subsequent uncontrolled release. However, some applications require the hydrogen be transported between a stationary, or static, part of the lithographic apparatus and a moving, or dynamic, part of the lithographic apparatus. In these applications, rigid tubing cannot be used due to the relative motion of the static and dynamic parts. Thus, flexible tubing must be used to accommodate the relative motion.
When using flexible tubing to carry hydrogen, a dual containment tube is used for safety reasons. A dual containment tube has a small inner tube surrounded by a larger tube. The inner tube transports the hydrogen, and the outer tube acts as back-up containment in case the inner tube leaks.
The conventional tubing arrangement is not without problems. Conventional dual containment tubing has an inner tube made of perfluoroalkoxy resin (PFA), and an outer tube made of fluorinated ethylene propylene resin (FEP). These materials are stiff and add resistance to the relative motion of the static and dynamic parts. These materials are also to prone to premature failure due to their stiffness, and are not suitable for applications having millions of movement cycles. The stiffness of these materials also provides the smallest conventional dual containment tubing with a minimum bend radius that is too large. The large bend radius leads to kinking of the tubing. The large bend radius also requires the tubing take up excessive volume that necessitates a separate assembly specifically to accommodate the limitations of the conventional tubing. The separate assembly also adds undesirable weight and unnecessary manufacturing cost to the lithographic apparatus. Further, conventional dual containment tubing fittings are not compatible with standard ultra-high purity (UHP) fittings, requiring the use of bulky and heavy adapters to adapt the incompatible fittings.
Therefore, the conventional systems and methods for transporting fluids between the stationary and the moving components suffer from significant disadvantages.